Advance tickets: $30
Same-day tickets: $20
Tickets sold: 55
Total money: $1300
Let us say that a represents the number of advance tickets sold, and s is the number of same-day tickets sold. Then, from the total number of tickets sold:

And for the total income:

From (1):

Using this result on (2):

Using this on (1'):

Number of advance tickets sold: 20
Number of same-day tickets sold: 35